Pediatric Dermatology

A Practical Overview of Pediatric Atopic Dermatitis, Part 1: Epidemiology and Pathogenesis

Cutis. 2016 April;97(4):267-271

Atopic dermatitis (AD) is a multisystem inflammatory disorder that is part of the spectrum of atopy, a series of conditions in which hyperreactivity and allergic symptoms are triggered by a series of causes including environmental allergens and irritants. Atopic dermatitis affects approximately one-quarter of children in developed countries and can have a negative impact on quality of life. In part 1 of this series addressing AD, the epidemiology and pathogenesis of AD are reviewed with an overview of skin barrier function. Later parts will address triggers, AD grading, differential diagnosis, comorbidities, and treatment options.

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Practice Points

The impact of atopic dermatitis (AD) on health-related quality of life mimics that of chronic childhood illnesses such as cystic fibrosis.
The prevalence of pediatric AD in the United States is estimated at more than 10% of children, with a 1.7 increased odds ratio in black children.
Diagnosis generally is made based on the presence of a pruritic eczematous eruption with typical morphology and a personal and/or family history of atopy.
Atopic dermatitis is caused by a complex interplay of skin barrier dysfunction and immune tendency toward allergy development.

References

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Atopic dermatitis (AD), or eczema, is the leading dermatologic diagnosis worldwide and is vexing to patients due to the itchiness of the rash. It is the leading cause of skin disease burden worldwide with a prevalence of 229,761,000 reported cases in 2010, presenting largely in preadolescence but also persisting through adulthood.¹ Using the children’s life quality index, it has been demonstrated that AD has a greater impact on health-related quality of life than renal disease and cystic fibrosis.² The overall burden of AD includes stress on the patient and his/her family as well as financial burdens that have been estimated to be similar to that of type 1 diabetes mellitus.³

Epidemiology of AD

The worldwide prevalence of AD varies by country and age group surveyed, with a higher prevalence in wealthy developed nations (eg, the United States) compared to poorer developing nations.⁴ Efforts to identify prevalence data for AD in the United States have been approached through a variety of strategies. A group in Oregon estimated the prevalence of AD in children aged 5 to 9 years to be 17.2% via a survey of parents (N=1465) and 11.8% with doctor-diagnosed eczema. In the same study, the question “Has a doctor ever said that your child has eczema?” was found to have a 91.3% predictive correlation.⁵ Analysis of the 2003 National Survey of Children’s Health demonstrated the overall US prevalence of pediatric AD to be 10.7% in 102,353 children 17 years or younger, with a range of 8.7% to 18.1% by region.⁶

In its evaluation of the worldwide prevalence of AD, the International Study of Asthma and Allergies in Childhood ranked the United States 17th.^7,8 The prevalence of AD in developed countries such as the United States is fluid and is expected to increase if the trends from the last 20 years remain true. In an assessment of the National Health Interview Survey data from 1997 to 2011 based on responses to the question, “During the past 12 months, has your child had eczema or any kind of skin allergy?”, the Centers for Disease Control and Prevention identified an increase in the prevalence of AD in patients aged 0 to 17 years from 7.4% in 1997-1999 to 12.5% in 2009-2011.⁹ Rising prevalence seems to be paired with rising incidence in the total number of severe intractable cases, reduced clearance at the approach of grade school, or cases persisting into adulthood.

Racial Disparity in AD

Racial disparity worldwide and migration are thought to contribute to the prevalence of and therapeutic need for AD. For example, in the United Kingdom, the prevalence of AD in London-born Afro-Caribbean children versus white children (total cross-section, N=693 [junior school children]) was 16.3% and 8.7%, respectively.¹⁰ In the United States, black children were more likely to have AD than white children (odds ratio, 1.7).⁶ Asian and black children also were more likely to present to a physician for treatment of AD than white children.^6,10-13

Definition and Diagnostic Considerations

According to Hanifin,¹⁴ “Eczema represents a family of inflammatory skin conditions characterized by pruritic, papulovesicular, sometimes weeping dermatitis. All demonstrate the histological hallmark of spongiosis, which helps to distinguish the eczemas from papulosquamous diseases such as psoriasis.”¹⁴ Atopic dermatitis is a variant of eczema; however, most laymen identify eczema and AD as being one and the same.

The Hanifin and Rajka¹⁵ criteria are the major diagnostic criteria for AD but are difficult to use in clinical practice. Three of the following 4 major criteria are needed for diagnosis: (1) pruritus, which is present universally; (2) typical morphology and distribution; (3) chronic or chronically relapsing dermatitis; and (4) personal and/or family history of atopy. Additionally, 3 of the following 23 minor criteria are needed for diagnosis: xerosis; ichthyosis vulgaris, palmar hyperlinearity, or keratosis pilaris; positive skin prick test; elevated serum IgE level; early age of onset; tendency toward cutaneous infections or impaired cell-mediated immunity; tendency toward nonspecific hand or foot dermatitis; nipple eczema; cheilitis; recurrent conjunctivitis; Dennie-Morgan fold (infraorbital fold); keratoconus; anterior subcapsular cataracts; orbital darkening; facial pallor or facial erythema; pityriasis alba; anterior neck folds; itching when sweating; intolerance to wool and lipid solvents; perifollicular accentuation; skin reactions from ingested foods or by food contact; environmental or emotional factors; and lesional/nonlesional white dermographism or delayed blanch.^15-1⁷

More pragmatic streamlined diagnostic criteria were established by Eichenfield et al.¹⁸ According to these guidelines, essential features for AD include pruritus and eczema. Important features seen in most cases and adding support to the diagnosis include early age of onset, atopy, and xerosis.¹⁸ In clinical practice, diagnosis is often made based on a pruritic relapsing condition in typical locations including the face, neck, and extensor surfaces in infants and children.